In recent years, photoelectric elements have been used in power generating devices which carry out photoelectric conversion, such as photoelectric cells and solar cells; light-emitting devices such as organic electroluminescent (EL) devices; optical display devices such as electrochromic display devices and electronic paper; and sensor elements which are sensitive to temperature, light or the like.
It is essential for the hole transporting layer in a photoelectric element to have high hole transporting properties. Moreover, the size of the surface area of the interface is important to this hole transporting layer. Here, “interface” refers to the interface between the hole transporting layer and a layer other than the hole transporting layer, at which interface holes are generated under the effects of energy from the exterior and which acts when holes are injected from the exterior. The hole transporting layer has hitherto been formed of a metal, organic semiconductor, inorganic semiconductor, conductive polymer, conductive carbon or the like.
For example, in photoelectric conversion elements, the hole transporting layer for transporting holes is formed of an organic material such as poly(3-hexylthiophene), triphenyldiamine (monomer, polymer, etc.), polyaniline, polypyrrole, polythiophene or a phthalocyanine compound. The conversion efficiency of photoelectric conversion elements is rising on account of the hole transporting abilities of such organic materials (see Patent Documents 1 to 3).
Also, it has been reported that, in the formation of a hole transporting layer for a molecular solar cell, a structure obtained by chemical bonding between an electron-donating molecule (donor) and an electron accepting molecule (acceptor) forms as a thin film on a substrate (see Non-Patent Document 1).
However, in the hole transporting layers reported in the above literature, sufficient hole transporting properties and a sufficient size of the interface for the function as a hole transporting layer have not both been achieved at once. Hence, there currently exists a desire for a hole transporting layer which has better hole transporting properties and also has a sufficiently large interface.    Patent Document 1: Japanese Patent Application Laid-open No. 2009-088045    Patent Document 2: Japanese Patent Application Laid-open No. 2009-065216    Patent Document 3: Japanese Patent Application Laid-open No. 2009-054936    Non-Patent Document 1: H. Imabori and S. Fukuzumi: “Bunshi taiyo denchi no tenbo [The outlook for molecular solar cells]”, Kagaku Kogyo, July 2001, p. 41